I\'ve seen a few ways to rewrite the $request_uri and add the index.html to it when that particular file exists in the file system, like so:
$request_uri
index.html
The solutions quoting $scheme://domain.com/ assume that the domain is hard-coded. It was not in my case and so I used:
$scheme://domain.com/
location / { ... rewrite index.html $scheme://$http_host/ redirect; ... }